1. Field of the Invention
The present invention relates generally to devices for electropolishing the inner surface of metal tubes and more particularly to such devices which utilize flexible electrodes drawn through the tube.
2. Description of the Prior Art
Metal tubing that is to be utilized in high purity applications is preferably cleaned by electropolishing prior to installation. Additionally, subsequent to installation, metal tubing utilized in many industrial applications may be attacked on the inner tubular surfaces by chemicals passing through the tubing. This may result in the need to replace the tubing, at great cost. Significant cost savings can be accomplished in many industrial equipment applications, if the interior surface of the metal tubing can be cleaned, such that the tubing can be reused.
Prior art devices are known that can clean the inner surface of straight tubing sections; however, tubing with a plurality of bends can pose a difficult problem. One such prior art device is described in U.S. Pat. No. 4,645,581, Apparatus for Electropolishing the Inner Surface of U-shaped Heat Exchanger Tubes, issued Feb. 24, 1987 to Voggenthaler et al. The present invention provides improved results.
Another problem which presents in the electropolishing of bent tubing, as well as tubing with extended straight runs, is keeping the tubing full of electrolyte solution during the electropolishing process. Gasses evolved by the electropolishing process accumulate and displace the electrolyte solution, thereby preventing the uniform electropolishing of the inner surface of the tubing. What is needed is a device that retains the electrolyte solution in the tubing, while facilitating the escape of the evolved gasses.
The tube inner surface electropolishing device includes an electrolyte delivery system to cause electrolyte to flow through the tube whose inner surface must be electropolished. An electrical cable having an electrode engaged to its distal end is slowly moved through the tube while an electrical current from a power supply passes through the electrode and the tube wall and the electrolyte flowing therebetween. Several electrode embodiments are disclosed including electrodes that include a chain of elements having alternating insulator and electrode elements, an electrode including a quantity of metallic wool enclosed in a permeable insulating member, and a flexible insulating member formed from a cylindrical tubular section which is axially compressible to produce a series of projecting flexible arms. The various electrode embodiments generally function such that the insulator members prevent electrically powered electrode elements from touching the sidewall and producing an electrical short.
The problem of keeping the tube full of electrolyte solution while facilitating the escape of trapped gasses is overcome in a particular embodiment of the present invention by attaching an electrolyte dam to the electrode. The electrolyte dam includes a body with a top and a bottom portion, a ballast fixed to the bottom portion, and a channel in the top portion. The body of the dam substantially occludes the lumen of the tube, keeping the tube full of electrolyte solution. The ballast maintains the upright position of the dam as it is drawn through the tubing, such that trapped gasses can escape through the channel in the top of the dam.
It is an advantage of the present invention that metal tubular components having a plurality of bends can be effectively, economically electropolished.
It is another advantage of the present invention that electrode embodiments are disclosed which are easy to manufacture and utilize.
It is a further advantage of the present invention that the various electrode embodiments are flexible to pass through a plurality of bends in a tubular member, such that complex tubular configurations can be effectively electropolished.
It is yet another advantage of the present invention that it provides an electrode embodiment that is compressible to allow it to pass through smaller openings, and then expand to process generally larger tubing.
These and other features and advantages of the present invention will be well understood by those skilled in the art upon review of the following detailed description. Further, those skilled in the art will recognize that various embodiments of the present invention may achieve one or more, but not necessarily all, of the above-described advantages. Accordingly, the listed advantages are not essential elements of the invention, and should not be construed as limitations on the scope of the present invention.